Fuel tanks for aircraft may have special shapes which make it difficult or impossible to measure the fuel level inside each fuel tank using a single probe. This applies in particular for fuel tanks which are situated in the wings of an aircraft. In addition the aircraft may vary in incline—also called attitude of the aircraft—and acceleration, so that a fuel level measurement result which is issued by one probe at a fixed location within the tank corresponds to varying fuel quantities depending on the aircraft attitude and acceleration. Because of these reasons, several probes are commonly implemented within an aircraft fuel tank.
Furthermore, it is commonly requested for aircraft design to provide two measurement chains which are independent from each other for measuring the fuel level which exists in an aircraft fuel tank during refuelling.
Combining such request with the issue of measuring the fuel level within a tank of complex shape leads to providing each fuel tank of an aircraft with a significant number of probes, typically between fifteen and eighty probes. This increases the resulting cost of the fuel gauging system, and also its weight. However, total weight is an important issue for aircraft since it increases the fuel consumption.
In addition, arranging probes with suitable connections is more difficult when the fuel tank and/or the aircraft wing are out of composite materials. This increases also the interest of reducing the probe number.
For example, U.S. Pat. No. 7,843,355 discloses a fluid gauging system for equipping one fuel tank, which comprises two separate subsets of probes distributed within the tank, and two separate processors. In refuelling operation mode, each probe subset is assigned to one of the processors, separately from the other probe subset and the other processor, so that each processor can infer fuel level information from the measurement signals which are issued by the probes of the corresponding subset. Thus, two results for the fuel level can be obtained independently and in parallel.
But such structure for a fluid gauging system is not optimized for an aircraft fuel tank although it meets the request for two measurement chains and can be adapted to any shape of the fuel tank.
Starting from this situation, one object of the present invention consists in providing a novel design for a fluid gauging system, which also meets the requirement for two measurement chains and can suit any shape for the fuel tank, but with less probes necessary.
Another object of the invention consists in providing a novel structure for a fluid gauging system, which allows savings in total weight.